In medical facilities or the like, for example, when administering medicinal solution such as an adhesion prevention agent or a body tissue adhesive agent to an affected area, the medicinal solution is discharged by using a syringe. In this case, the medicinal solution diluted or dissolved with liquid is sucked into and fills the outer cylinder of the syringe by moving the plunger in the direction toward a proximal end of the outer cylinder, and the medicinal solution is discharged from a flowing port provided at a distal end of the outer cylinder by moving the plunger in the direction toward the distal end of the outer cylinder.
In the syringe configured in this manner, a configuration is required so that the plunger cannot be pulled out from the outer cylinder (cannot be moved in the direction toward the proximal end) in a state in which the outer cylinder is filled with the medicinal solution (liquid). If the plunger is pulled out, there is a probability that non-filled substance (for example, air, gas, and the like) of an external environment enters the interior of the outer cylinder and causes contamination or deterioration of the filled liquid. In addition, if the plunger comes apart from the outer cylinder by being pulled out, the filled liquid may inconveniently spill out.
Japanese Application Publication No. 8-504352 discloses a structure to prevent the movement of the plunger in the direction toward the proximal end that includes a tooth portion (ratchet gear) on a side surface of the plunger and a movement stop device configured to engage the tooth portion. Accordingly, the movement stop device locks the tooth portion and hence the movement of the plunger inserted into the outer cylinder in the direction toward the proximal end is prevented.
However, from the syringe disclosed in JP-T-8-504352, a method of movement of the plunger when filling the outer cylinder with liquid cannot be estimated. In other words, since the tooth portion is locked to the movement stop device in the configuration of the syringe disclosed in JP-T-8-504352, the movement of the plunger in the direction toward the proximal end which is performed when filling the syringe with the liquid cannot be performed easily.